Those suffering from severe depression may reap the benefits of low-intensity interventions, including self-help books and websites, says a new study from researchers at the University of Manchester in England.

For the study, the researchers reviewed data from 16 previous studies involving 2,470 participants. Overall, they found that those with severe depression reported a four to five point drop in overall symptoms in surveys. This was roughly the same drop as those with minor depression.

"Clearly some patients will not find such interventions useful, and it would seem sensible to continue to refer some cases to more intense psychological intervention or pharmacological management until further evidence is generated confirming our findings," the researchers wrote in their study report. "The current data suggest that the threshold could be relatively high if patients are willing to engage in low-intensity interventions."